US6667366B2 - Chemical modification of the surface of natural fibers - Google Patents

Chemical modification of the surface of natural fibers Download PDF

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Publication number
US6667366B2
US6667366B2 US09/897,984 US89798401A US6667366B2 US 6667366 B2 US6667366 B2 US 6667366B2 US 89798401 A US89798401 A US 89798401A US 6667366 B2 US6667366 B2 US 6667366B2
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group
process according
fibers
natural fibers
fiber
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US20020086938A1 (en
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Mariastella Scandola
Sergio Sandri
Massimo Baiardo
Giovanna Frisoni
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Universita di Bologna
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Universita di Bologna
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Assigned to UNIVERSITA' DEGLI STUDI DI BOLOGNA reassignment UNIVERSITA' DEGLI STUDI DI BOLOGNA ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: BAIARDO, MASSIMO, FRISONI, GIOVANNA, SANDRI, SERGIO, SCANDOLA, MARIASTELLA
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
    • C08B11/00—Preparation of cellulose ethers
    • C08B11/02—Alkyl or cycloalkyl ethers
    • C08B11/04—Alkyl or cycloalkyl ethers with substituted hydrocarbon radicals
    • C08B11/08—Alkyl or cycloalkyl ethers with substituted hydrocarbon radicals with hydroxylated hydrocarbon radicals; Esters, ethers, or acetals thereof
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G81/00—Macromolecular compounds obtained by interreacting polymers in the absence of monomers, e.g. block polymers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/04—Reinforcing macromolecular compounds with loose or coherent fibrous material
    • C08J5/06—Reinforcing macromolecular compounds with loose or coherent fibrous material using pretreated fibrous materials
    • D—TEXTILES; PAPER
    • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
    • D06M15/00—Treating fibres, threads, yarns, fabrics, or fibrous goods made from such materials, with macromolecular compounds; Such treatment combined with mechanical treatment
    • D06M15/19—Treating fibres, threads, yarns, fabrics, or fibrous goods made from such materials, with macromolecular compounds; Such treatment combined with mechanical treatment with synthetic macromolecular compounds
    • D06M15/37—Macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
    • D06M15/53—Polyethers
    • D—TEXTILES; PAPER
    • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
    • D06M2101/00—Chemical constitution of the fibres, threads, yarns, fabrics or fibrous goods made from such materials, to be treated
    • D06M2101/02—Natural fibres, other than mineral fibres
    • D06M2101/04—Vegetal fibres

Definitions

  • the present invention relates to a polymer-grafted fiber used to make composite materials.
  • the invention relates in particular to a method for making such polymer-grafted natural fibers.
  • Composites consist basically of two distinct phases: a first continuous phase (matrix) and a second dispersed phase.
  • the continuous phase (matrix) is a polymer.
  • a second component is dispersed in the first continuous phase to make the second dispersed phase.
  • the dispersed phase in composites is usually designed to improve the mechanical properties of the matrix.
  • the dispersed phase may have very different properties, form and dimensions, depending on the specific function it has to perform within the composite.
  • Fibers such as, for example, glass, carbon or synthetic polymer fibers.
  • Composites consisting of a polymer matrix with natural fibers as the reinforcing agent have only recently been introduced.
  • the natural fibers most used for this purpose are of plant origin, and in particular, cellulose fibers.
  • the adhesion between the continuous phase (matrix) and the dispersed phase (fiber) must be optimized, since the mechanical load applied to the matrix must be effectively transferred to the fiber.
  • it is the fiber component that confers the good mechanical properties.
  • the effectiveness of the adhesion at the interface between fiber and matrix depends largely on the surface properties of both components. Usually, the surface properties are correlated to parameters such as surface tension and polarity.
  • the surface properties of the polymer matrices currently available on the market, used in the preparation of composites, are very different from the surface properties of natural fibers.
  • the surface tension and polarity of the two components must be very similar.
  • the continuous phase (matrix) or the dispersed phase (fiber) can be chemically modified in numerous ways to suitably change the surface properties.
  • One way of chemically modifying the surface of a fiber is by grafting polymer chains onto it.
  • a fiber can be grafted with polymer chains which polymerize in situ or with ready-made polymer chains.
  • the second process allows polymer chains of different types and preset length to be grafted.
  • U.S. Pat. No. 3,492,082 discloses a process for the preparation of polymer-grafted cellulose fibers.
  • U.S. Pat. No. 3,492,082 describes a free-radical type, in situ polymerizing process.
  • the free-radical polymerization produces on the fiber grafted chains with a very wide length distribution.
  • the chain length of the polymer grafts thus varies considerably and cannot be predetermined.
  • the kinetics of the free radical grafting reaction are difficult to control.
  • U.S. Pat. No. 4,857,588 describes a process in which the cellulose material is first treated with an aqueous sodium hydroxide solution. The cellulose material is then treated with sodium methoxide in methanol in order to convert the hydroxyl groups of cellulose into salified oxy groups with sodium in a quantity ranging from 0.25 to 33.3%.
  • the resulting cellulose material is contacted with a ready-made organic compound having a chain with an electrophilic functional group at one end.
  • one of the aims of the present invention is to provide natural fibers whose surface properties are modified in such a way as to obtain composite materials having improved mechanical properties.
  • Another aim of the present invention is to provide a process for the preparation of polymer-grafted natural fibers which leaves the mechanical properties of the fiber unchanged.
  • the present invention provides a process for the preparation of polyether-grafted natural fibers.
  • the invention also relates to a polyether-grafted natural fiber, as described in the corresponding independent claim, made preferably but not necessarily using the process according to the present invention.
  • the polyether-grafted natural fiber according to the present invention is highly compatible with the polymer matrices of numerous composite materials. Its surface properties are modified to improve the adhesion between it and the matrix of the composite material. Further, since only the surface structure of the natural fiber is modified, the body of the grafted fiber remains unchanged and maintains its mechanical resistance. The resulting composite material therefore has better mechanical properties than composite materials known up to now.
  • the present invention further relates to the use of polyether-grafted natural fibers made preferably but not necessarily using the process according to the present invention for the preparation of composite materials, as described in the corresponding independent claim.
  • the natural fibers used in the preparation of the composite materials are cellulose fibers prepared according to the process taught by the present invention.
  • FIG. 1B shows a wide-angle X-ray diffraction spectrum of a fiber that was pre-treated in NaOH 5 N according to the teachings of prior art
  • FIGS. 2A and 2B show, respectively, the changes in the polarity and surface tension of the cellulose with changing in both degree of substitution (DS) and molecular weight (MW) of the polyether graft (in this case, polyethylene oxide).
  • DS degree of substitution
  • MW molecular weight
  • natural fibers denotes any natural fibers having on their surfaces hydroxyl groups on which a ready-made polymer chain can be grafted.
  • the fibers used are preferably the cellulose fibers of certain plants. Of these, cotton, flax and hemp fibers are preferred.
  • the pre-treated fibers are contacted with a first solution comprising an alkaline reagent.
  • the first solution comprises an anhydrous solvent such as, for example, tetrahydrofuran (THF) and an alkali such as, for example, potassium-tert-butylate and a crown ether such as 18-crown-6.
  • the potassium-tert-butylate and the crown ether are present preferably in equimolar quantities.
  • the quantity of potassium-tert-butylate exceeds the total quantity of hydroxyl groups of the natural fiber.
  • the reaction occurs in an anhydrous environment in an inert atmosphere.
  • the natural fibers are preferably allowed to react with the solution for a time ranging from 1 to 6 hours and at a temperature in the range of from 30° C. to 80° C.
  • potassium-tert-butylate with 18-crown-6 is advantageous because the crown ether acts as a phase transfer agent since it protects the potassium cation and at the same time makes it available for the alcoholate.
  • This step is designed to activate the natural fibers before grafting the polyether chains on the salified oxy groups.
  • the first solution comprises an anhydrous solvent, such as, for example, methyl alcohol and an alkali such as, for example, sodium methylate.
  • anhydrous solvent such as, for example, methyl alcohol and an alkali such as, for example, sodium methylate.
  • the reaction occurs in an anhydrous environment in an inert atmosphere.
  • the natural fibers are preferably allowed to react with the solution for a time ranging from 1 to 48 hours and at a temperature in the range of from 20° C. to 80° C.
  • the hydroxyl groups in the natural fibers are converted into alcoholates via the alkaline reagent.
  • the alcoholates are in the salified form with the cation of the alkali used: in this case, the cation is the sodium cation.
  • This step is another way of activating the natural fibers before grafting the polyether chains on the salified oxy groups.
  • the process comprises a further, filtering step.
  • the solution containing the natural fibers and the sodium methylate is filtered in order to remove the solvent and reagent dissolved in it.
  • the solvent and the reagent consist, for example, of methyl alcohol and sodium methylate.
  • the polyether chains are ready-made before being grafted on the activated fiber.
  • the polyether is one having an aliphatic or aliphatic/aromatic group at one end and a leaving group at the other end.
  • the polyether having the general formula (I), is a polyether functionalized by a group that favors nucleophilic substitution (a good leaving group):
  • n 1 and 200
  • R is an aliphatic or aliphatic/aromatic group
  • Y is a functional leaving group
  • n is between 1 and 20;
  • R2 is either hydrogen or a linear or branched C1-C4 alkyl group
  • R1 is the same as or different from R2 and is either hydrogen or a linear or branched C1-C4 alkyl group
  • n may be between 1 and 200, but ideally, m is between 4 and 60.
  • the aliphatic R group is either a linear or branched C1-C4 alkyl group.
  • the aliphatic/aromatic R group is a benzyl group.
  • n may be between 1 and 20, but ideally, n is between 2 and 5.
  • R1 may be the same as or different from R2 and may be either hydrogen or a linear or branched aliphatic group.
  • R1 and/or R2 are either hydrogen or a linear or branched C1-C4 alkyl group.
  • the ring presents two substituting groups between positions a), b), c) and d).
  • linear or branched C1-C4 alkyl group means a methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl or tert-butyl group.
  • the polyether of general formula (I) has at its two ends an R and a Y group.
  • the Y group is a functional leaving group which favors nucleophilic substitution.
  • the polyethers of general formula (I) are polyoxyethylene R—(O—OH 2 —CH 2 ) m —Y or polyoxy-propylene R—(O—CH 2 —CH 2 CH 2 —) m —Y.
  • the pre-treated and activated natural fibers can be reacted with the polyether in the presence of an anhydrous solvent at a temperature within a range of from 30° C. to 80° C. for a time of between 1 and 24 hours.
  • the reaction is made at a temperature in a range of from 60° C. to 80° C.
  • the polyether derivative is grafted onto the activated natural fibers.
  • the polyether of general formula (I) reacts with the salified alcoholate to yield Cell —O—[X—O] m —R.
  • the polyether On being grafted onto the fiber, the polyether loses the leaving Y group.
  • the solution is heated to a temperature of 70° C. in an inert atmosphere.
  • This solution (sol. 2) is added to the reactor (sol. 1) and allowed to react for 5 hours at 70° C.
  • the reaction is extinguished with water.
  • the fibers are filtered and washed in abundant water, acetone and ethyl ether and then dried under vacuum at 80° C. for 16 hours.
  • the fibers are dried under vacuum for 16 hours at 80° C.
  • the solution is heated to a temperature of 70° C. in an inert atmosphere.
  • the reaction is extinguished with water.
  • the fibers are filtered and washed in abundant water, acetone and ether and then dried under vacuum at 100° C. for 16 hours.
  • the fibers are dried under vacuum for 16 hours at 80° C.
  • This solution (sol. 2) is added to the reactor (sol. 1) and allowed to react for 3 hours at 70° C.
  • the fibers are filtered and washed in abundant water, acetone and ether and then dried under vacuum at 80° C. for 16 hours.
  • the natural fibers treated using the process according to the present invention were analyzed by TOF-SIMS (Time of Flight Secondary Ion Mass Spectrometry) in order to check the fiber surface for polyether chains. This technique measures the mass of the ion fragments that peel off the surface as a result of ion bombarding.
  • the fibers treated according to the present invention show TOF-SIMS signals typical of the fragmentation products of the polyether grafts.
  • the micro and macro structural characteristics of the natural fibers treated according to the process of the present invention were analyzed using a scanning electron microscope and wide-angle X-ray diffraction. The result is shown in FIG. 1 A.
  • a solution (a) containing 60 mM of a poly(oxyethylene) of the formula CH 3 —(—O—CH 2 —CH 2 —) n —OH, with n 16 and molecular weight 750 in 100 ml of CH 2 Cl 2 and 75 mM of triethylamine is prepared.
  • the solution (b) is added to the solution (a) dropwise.
  • the reaction is maintained at 0° C. for 3 hours.
  • the triethylamine chlorohydrate precipitates. Water is added and the triethylamine chlorohydrate solubilizes.
  • the organic phase is separated. Subsequently, the organic phase is concentrated in volume.
  • the liquid organic phase contains CH 3 —(—OCH 2 —CH 2 —) 16 —O—SO 2 —CH 3 which will be used to graft the natural fibers according to the process of the present invention.
  • a solution containing 54 mM of mesylate, as pre-pared in example 4, in 100 ml of acetone is prepared.
  • the sodium iodide solution is added to the mesylate solution dropwise and the reaction maintained for 48 hours. This yields a pale yellow solution containing sodium methanesulphonate salt (CH 3 —SO 3 —Na) Subsequently, the solution is filtered and concentrated, diluted in methylene chloride and washed with an aqueous solution of Na 2 S 2 O 3 . The solution, concentrated again, contains the poly(oxyethylene) mono-methyl-ether iodide which will be used to graft the natural fibers according to the process of the present invention.
  • the process according to the present invention has several advantages.
  • the first advantage is in that the process chemically modifies mainly the outer surface of the natural fibers to improve the adhesion between fiber and polymer matrix in composite materials. Improved adhesion between fiber and polymer matrix yields a composite material with improved mechanical properties.
  • the fibers grafted using the process taught by the present invention have numerous applications in the field of polymer matrix composites where the reinforcing phase consists of natural fibers from renewable sources and not glass fibers and/or synthetic fibers.
  • the fibers treated according to the process taught by the present invention differ considerably from the same fibers treated using the processes taught by prior art. Indeed, unlike fibers treated according to prior art, fibers treated with the process of the present invention maintain their original fiber structure. Furthermore, the surface properties differ from those of fibers yielded by known processes since the polymer grafts themselves are different and the surface properties depend directly on the type of polymer grafts.
  • the surface tension and polarity values for the polymer families which can be used as matrices in composite materials are lower than the value for cellulose.
  • FIGS. 2A and 2B show the changes in the polarity and surface tension of the cellulose with the changes in both the degree of substitution (DS) and molecular weight (MW) of the polyether graft (as an example, the two figures show the changes of ⁇ and ⁇ for chains of polyethylene oxide with molecular weight 350, 750 and 2000). The values shown were calculated using the group contribution method. They are not experimental data.
  • Polyethylene oxide was chosen because it presents a good level of compatibility with numerous polymers.
  • the polyether chains which are grafted on the activated natural fibers are ready-made chains.
  • the use of ready-made polyether chains makes it possible to use chain grafts whose molecular weight is predetermined according to the extent of the variation that is desired in the surface properties (especially hydrophilicity) of the fiber.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Biochemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Textile Engineering (AREA)
  • Treatments For Attaching Organic Compounds To Fibrous Goods (AREA)
US09/897,984 2000-07-05 2001-07-05 Chemical modification of the surface of natural fibers Expired - Fee Related US6667366B2 (en)

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EP00830474 2000-07-05
EP00830474A EP1170415B8 (de) 2000-07-05 2000-07-05 Chemische Oberflächenmodifizierung von Naturfasern

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20080108772A1 (en) * 2006-11-08 2008-05-08 Ntnu Technology Transfer As Nanocomposites based on cellulose whiskers and cellulose plastics

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008098037A2 (en) * 2007-02-06 2008-08-14 North Carolina State University Polymer derivatives and composites from the dissolution of lignocellulosics in ionic liquids
JP5614402B2 (ja) * 2009-06-12 2014-10-29 三菱化学株式会社 修飾セルロース繊維及びそのセルロース複合体
WO2011126038A1 (ja) * 2010-04-06 2011-10-13 ユニチカ株式会社 ポリアミド樹脂組成物及びポリアミド樹脂組成物の製造法
IN2013MU03000A (de) * 2013-09-16 2015-07-10 Sp Advanced Engineering Materials Private Ltd
CN113546474B (zh) * 2020-04-26 2022-12-09 淄博东森石油技术发展有限公司 一种用于分离乳化聚四氟乙烯体系的分离材料及其装置
CN117682837B (zh) * 2023-12-19 2026-01-30 东北农业大学 一种大麻纤维建筑材料的制备方法

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2109295A (en) 1934-05-17 1938-02-22 Ici Ltd Textile fabric and process of making the same
US3492082A (en) 1965-11-15 1970-01-27 Stevens & Co Inc J P Graft copolymers and methods of preparation thereof
GB1590176A (en) 1976-08-20 1981-05-28 Hoechst Ag Cellulose hydrate structures and processes for their manufacture
US4803116A (en) * 1985-10-31 1989-02-07 Toray Industries Incorporated Waterproof fabric having high moisture permeability and method of making same
US4857588A (en) 1986-07-02 1989-08-15 Shell Oil Company Process for the preparation of hydrocarbyl-grafted cellulose fibers
DE4440246A1 (de) 1994-11-11 1996-05-15 Thueringisches Inst Textil Faserverbundwerkstoff und Verfahren zu seiner Herstellung

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2109295A (en) 1934-05-17 1938-02-22 Ici Ltd Textile fabric and process of making the same
US3492082A (en) 1965-11-15 1970-01-27 Stevens & Co Inc J P Graft copolymers and methods of preparation thereof
GB1590176A (en) 1976-08-20 1981-05-28 Hoechst Ag Cellulose hydrate structures and processes for their manufacture
US4803116A (en) * 1985-10-31 1989-02-07 Toray Industries Incorporated Waterproof fabric having high moisture permeability and method of making same
US4857588A (en) 1986-07-02 1989-08-15 Shell Oil Company Process for the preparation of hydrocarbyl-grafted cellulose fibers
DE4440246A1 (de) 1994-11-11 1996-05-15 Thueringisches Inst Textil Faserverbundwerkstoff und Verfahren zu seiner Herstellung

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20080108772A1 (en) * 2006-11-08 2008-05-08 Ntnu Technology Transfer As Nanocomposites based on cellulose whiskers and cellulose plastics

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US20040064900A1 (en) 2004-04-08
DE60020107D1 (de) 2005-06-16
DE60020107T2 (de) 2006-01-26
ATE295444T1 (de) 2005-05-15
US20020086938A1 (en) 2002-07-04
EP1170415A1 (de) 2002-01-09
EP1170415B1 (de) 2005-05-11
EP1170415B8 (de) 2005-06-29

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